1. Field of the Invention:
This invention relates to a braking system for vehicle, and more particularly to a braking system for vehicle in which the transmission of the pulsating pressure from the brake circuit to the fluid-pressure generating source or master cylinder is limited.
2. Description of the Prior Art:
For example, the Japanese Patent Opening Gazzette No. 142733/1981 discloses the braking system for vehicle which includes: a brake fluid pressure generating source: a brake-applying apparatus for braking a wheel or wheels with the brake fluid pressure supplied from the brake fluid pressure generating source; a pulsating-pressure absorbing apparatus arranged between the brake fluid pressure generating source and the brake-applying apparatus; and throtting means arranged in the pulsating-pressure absorbing apparatus, for limitting the brake fluid flowing from the side of the brake-applying apparatus towards the brake fluid pressure generating source. Or it discloses the braking system for vehicle which includes; a master cylinder: a wheel cylinder for braking a wheel with the brake fluid pressure supplied from the master cylinder; an anti-skid control valve apparatus being arranged between the master cylinder and the wheel cylinder and changed over in accordance with the instructions generated from a control unit for evaluating or measuring a skid condition or behavior of the wheel; a brake relieving circuit one end of which communicates with the master cylinder and another and of which communicates with the anti-skid control valve apparatus, a fluid pressure pump being arranged in the brake relieving circuit, for pressurizing and returning the brake fluid discharged through the anti-skid control valve apparatus from the wheel cylinder; a pulsating-pressure absorbing apparatus being arranged between the fluid pressure pump and the master cylinder, for limitting the transmission of the pulsating pressure of the fluid pressure pump; and throtting means arranged in the pulsating-pressure absorbing apparatus, for limitting the brake fluid flowing from the side of the fluid pressure pump towards the master cylinder. In the above-described braking system, the throttle is fixed. It limits the transmission of the pulsating pressure of the fluid pressure pump, to the master cylinder. Further, there is provided a check valve which inhibits brake fluid from flowing towards the master cylinder from the fluid pressure pump side. Accordingly, a second check valve is required for brake-relieving, and it permits brake fluid to flow from the wheel cylinder side to the master cylinder side.
Further in the above-described braking system, it is preferable that the throttle is arranged nearer to the master cylinder and that the distance between the generating source of the pulsating pressure and the throttle, and the volume of the conduit between them is larger, since the transmission of the pulsating pressure of the fluid pressure pump or of the pulsating pressure generating in the brake circuit, to the master cylinder can be effectively decreased. Accordingly, it is considered that the throttle is arranged at the outlet of the master cylinder. However, the throttling effect occurs both on the braking application and on the brake relief. The throttle has bad influence both on the braking application and on the brake relief. Accordingly, it is required that the throttle is effective only for the fluid flowing towards the master cylinder, and a check valve which permits fluid to flow out from the outlet of the master cylinder, is provided. In that case, another check valve for brake relieving is required.
Thus, the braking system for vehicle is large-sized and complicated. The conduit construction is complicated, too. The assembling step is troublesome.